Various proposals have been made to improve the cornering performance of road vehicles. One example can be found in the electric power steering device which minimizes the effort required for the vehicle operator to steer the vehicle by providing a steering assist torque using an electric motor. It has also been proposed to detect the dynamic states of the vehicle such as the lateral acceleration and the yaw rate by using appropriate sensors, and to apply a reactive steering torque by using an electric power steering device so as to control such dynamic states. For such a reactive steering control, reference should be made to U.S. Pat. Nos. 5,528,497, 5,703,775, and 5,774, 819 which are assigned to the common assignee, and the contents of these patents are hereby incorporated in this application by reference.
According to yet another proposal, the distribution of the traction and/or braking force between the right and left wheels is changed as desired so as to apply a yaw moment to the vehicle. It can be favorably utilized to improve the maneuverability and stability of the vehicle. For such a torque splitting arrangement, reference should be made to U.S. Pat. No. 5,692,987 which is assigned to the common assignee, and the contents of this patent are hereby incorporated in this application by reference.
According to the proposal to control the distribution of the traction and/or braking force between the right and left wheels, it was however found that a certain steering torque is produced when the right and left wheels are subjected to different traction and/or braking forces. This phenomenon which is sometimes called as torque steer is due to the uneveness in the moment around the kingpin between the right and left wheels as illustrated in FIG. 6, and can be eliminated by changing the suspension geometry so that the traction or braking force would not produce a moment around the kingpin. This however significantly complicates the design of the wheel suspension system, and reduces the freedom in design.